The present invention relates to light weight vehicle wheels and more particularly to vehicle wheels composed of two or more separately formed parts and a method for forming the same.
Today there are mainly three types of light metal wheels on the market: a cast one-piece, a forged one-piece, and welded plate wheels. The forged and welded types have the biggest potential for low weight because of the use of wrought alloys having higher strength than casting alloys. However, casting gives a higher design freedom, without substantially influencing the cost. The design freedom does not only give styling flexibility, but also makes it possible to give the center part of the wheel a nearly optimal shape with respect to cornering strength which normally is the critical aspect for this part.
In the rim area, however, an alloy with high mechanical strength and good elongation is of primary importance. An optimal design of a wheel in order to obtain low weight and full styling freedom thus seems to be one where a cast center part is joined to a rim of wrought alloy. Such wheels are already on the market and have joints either comprising a bolted connection (being an expensive and non-low-weight solution) or a weld seam.
However, all known disclosed welding methods for wheels are based on fusion welding (e.g., arc welding) or friction welding which requires joint preparation and post weld dressing steps, which negatively influences the total manufacturing costs. Furthermore, several other negative/limiting aspects have been experienced, such as the environmental hazard connected with fusion welding, problems with dimensional stability both with fusion and friction welded wheels, and limited design freedom with regard to the need for performing multiple parallel welds compared to conventional friction welding processes.
It is therefore an object of the present invention to provide a new and improved type of two-piece wheel which avoids the above drawbacks related to the presently applied joining methods.
Another object of the present invention is to provide a new method for joining of separately formed wheel parts offering the possibility to achieve high quality weld seams.
These and other objects and advantages of the present invention will be met by the provisions of a new method of joining separately formed wheel parts and a novel automotive light metal wheel.